Communication and collaborative research pattern of Sivaraj Ramaseshan: A scientometric portrait

S. Ramaseshan has contributed for the better understanding of various subjects in which he specialized during his years at the Indian Institute of Science, University of Madras and the Raman Research Institute. In this paper we would like to emphasis on his scientific contributions in various journals and some classic papers. In his entire career as a scientist he has collaborated with 47 eminent scientists and students and has published a total of 178 papers during the years 1944–2000. His field of interest has been varied and thus classified into 4 main area, i.e.: Crystallographic studies, Magneto-optics & Optics, Solid State Physics and Miscellaneous topics.     

Synthesis, and measurement of structural and magnetic properties, of La1-xNaxFeO3(0.0≤x≤0.3) perovskite oxides

Polycrystalline La_1-xNa_xFeO₃ (0.0≤x≤0.3) solid solutions were synthesized by a solution combustion method using glycine as a fuel. The combustion synthesized compounds were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), diffused reflectance (DR) in the UV-vis, and magnetic measurements. The crystal structure examined by X-ray powder diffraction indicated that the samples were single phase and crystallized in an orthorhombic (space group, Pbnm no.62) structure. The parent and sodium-substituted compounds showed canted anti-ferromagnetic behavior associated with an increase in magnetic moment as Na content increased. The changes in magnetic properties of the materials were correlated to the changes in structural features, as shown by Rietveld structural refinement of the materials.     

Development of Nitrendipine Controlled Release Formulations Based on SLN and NLC for Topical Delivery: In Vitro and Ex Vivo Characterization

The aim of the investigation is to develop solid lipid nanoparticles (SLN) and nano-structured lipid carrier (NLC) as carriers for topical delivery of nitrendipine (NDP). NDP-loaded SLN and NLC were prepared by hot homogenization technique followed by sonication, and they were characterized for particle size, zeta potential, entrapment efficiency, stability, and in vitro release profiles. Also the percutaneous permeation of NDPSLN A, NDPSLN B, and NDPNLC were investigated in abdominal rat skin using modified Franz diffusion cells. The steady state flux, permeation coefficient, and lag time of NDP were estimated over 24 h and compared with that of control (NDP solution). The particle size was analyzed by photon correlation spectroscopy (PCS) using Malvern zeta sizer, which shows that the NDPSLN A, NDPSLN B, and NDPNLC were in the range of 124–300 nm during 90 days of storage at room temperature. For all the tested formulations (NDPSLN A, NDPSLN B, and NDPNLC), the entrapment efficiency was higher than 75% after 90 days of storage. The cumulative percentage of drug release at 24 h was found to be 26.21, 30.81, and 37.52 for NDPSLN A, NDPSLN B, and NDPNLC, respectively. The results obtained from in vitro release profiles also indicated the use of these lipid nanoparticles as modified release formulations for lipophilic drug over a period of 24 h. The data obtained from in vitro release from NDPSLN A, NDPSLN B, and NDPNLC were fitted to various kinetic models. High correlation was obtained in Higuchi and Weibull model. The release pattern of drug is analyzed and found to follow Weibull and Higuchi equations. The permeation profiles were obtained for all formulations: NDPSLN A, NDPSLN B, and NDPNLC. Of all the three formulations, NDPNLC provided the greatest enhancement for NDP flux (21.485 ± 2.82 μg/h/cm²), which was fourfold over control (4.881 ± 0.96 μg/h/cm²). The flux obtained with NDPSLN B (16.983 ± 2.91 μg/h/cm²) and NDPNLC (21.485 ± 2.82 μg/h/cm²) meets the required flux (16.85 μg/h/cm²).     

Synthesis,Characterization, Luminescent and Thermal Properties of a Hybrid Inorganic–Organic Polymeric Framework Formed by Lead (II) Pyridinecarboxylate

Abstract  

A coordination polymer of formula [Pb_0.5(pyc)] _n , 1, where Hpyc = pyridine-3-carboxylic acid, has been synthesized and structurally characterized by X-ray single crystal diffraction analysis. Every Pb(II) centre demonstrate trigonal dodecahedron geometry. The ligand i.e. pyridine-3-carboxylate offers μ _{3 -} η ² : η ¹ coordination pattern using its hetero donor centres. The complex initially forms an infinite 1D chain (c-axis) which is turned to 2D sheet and finally a 3D network is recognized through ligand connectivity. Stabilization of 3D structure is further reinforced by π–π stacking interaction. An open channel is identified along c-axis. TG analysis has been performed for the complex. Emission study demonstrates the existence of intraligand and metal-to-ligand charge transfer transition in 1.     

EFFECT OF INTERPHASE MASS TRANSFER ON UNSTEADY CONVECTTVE DIFFUSION: PART II HAGEN POISEUILLE FLOW OF A POWER LAW FLUID IN A TUBE

The influence of interphase mass transfer on dispersion of solute in a tube flow of a power-law fluid is examined at all times after the injection of the solute. Three important dispersion mechanisms are shown to arise in the study in place of two in classical studies. This is true in channel flows also (see Siddheshwar et al. [1]). The present analytical result on dispersion of solute with wall catalysed reaction at long times is compared with the analytical solution when reaction is absent. The Taylor [2] and Aris [2] of dispersion are obtained as limiting cases from the study. The graphical results of the study serve as a jury on any numerical treatment of the present problem that might be undertaken considering non-asymptotic all-time analysis.     

Deriving cropping system performance indices using remote sensing data and GIS

The cropping system approach is a holistic management of variant and invariant resources to optimize the food production. Various indices are used to assess and evaluate the efficiency and sustainability of the systems. These indices are generally computed from the data collected by traditional survey methods that are time consuming and non‐spatial. An attempt has been made to derive such indices using satellite remote sensing data for the state of West Bengal, India. Three indices—Multiple Cropping Index (MCI), Area Diversity Index (ADI) and Cultivated Land Utilization Index (CLUI)—were attempted. Multi‐date, multisensor data from Indian Remote Sensing Satellite (IRS) and Radarsat Synthetic Aperture Radar (SAR) were used to derive cropping pattern, crop rotation, and crop calendar. Crop type, acreage, rotation and crop duration were used as inputs to compute the indices at district and state level. The indices were categorized as high, medium and low to evaluate the performance of each of the 16 districts. The average MCI of the state derived was 140. At district level it varied from 104 to 177. The average ADI of state was 2.5 and varied from 1.5 to 5.0.     

Solving general multi-class closed queuing networks using parametric decomposition

This paper presents a new approach to evaluate the performance of general multi-class closed queuing networks. The approach uses parametric characterization of the traffic processes to derive two-moment approximations for performance measures at individual nodes. Based on these approximations, linkage equations are derived to establish the relationships between the various nodes in the network. These relationships result in a system of non-linear equations that is solved using an iterative procedure. Numerical studies comparing the performance of the approach with detailed simulations suggest that the approach yields fairly accurate estimates of performance measures without significant computational complexity.